They picked up a weak signal from the rover Spirit. They intend to send it several commands to try to find out more about why it stopped working.

Spirit was 19 days into a three-month mission when it stopped communicating with Earth on Wednesday.

Meanwhile, European orbiter Mars Express has sent back some amazing images of the planet's surface.

They show evidence that water once existed on the planet.

There are pictures of what appear to be valleys created by the flow of rivers.

The images are of a very high quality - even showing dust blowing over the rims of craters.

Before it broke down, Spirit also took some stunning pictures - this time from the surface of Mars.

The breakdown meant scientists could only hear a faint beep - indicating there was a serious problem with the rover's computer.

Twin rover

Spirit's twin rover - called Opportunity - is set to land on Mars at the weekend.